Liquid crystal display apparatuses have space-saving and power-saving features. In addition, liquid crystal display apparatuses have been recently improved in performance such as viewing angle, contrast, color reproducibility, response speed, and the like. This has caused liquid crystal display apparatuses to outperform cathode-ray tubes. Therefore, it is predicted that liquid crystal display apparatuses will be applied more and more widely to televisions and OA monitors (computer monitors) in the future.
Normally, when a voltage is applied to a liquid crystal cell, the long axis direction (director) of liquid crystal material (liquid crystal molecules) contained in the liquid crystal cell is changed due to the dielectric anisotropy of the liquid crystal material. The liquid crystal material has optical anisotropy. Therefore, a change in direction of the liquid crystal material causes a change in direction of polarization of light passing through the liquid crystal cell. Moreover, with the functions of a polarization plate and other members that are provided in the liquid crystal cell function, the amount of light that passes through the liquid crystal cell is controlled in accordance with an applied voltage applied to the liquid crystal cell (applied voltage). This makes it possible to set the luminance of each pixel to a desired gradation luminance, thereby making it possible to display an image.
However, it takes a certain amount of time for the liquid crystal material to respond to a change in applied voltage (the liquid crystal material has a low response speed). For example, in case of a currently widely used liquid crystal display method (liquid crystal display mode) such as TN (Twisted Nematic), IPN (In-Plane-Switching), or VA (Vertically Aligned), the liquid crystal material has a response speed of 30 msec to 50 msec between slow gradations. This makes it impossible to realize a response speed that corresponds to 60 Hz (approximately 16.6 msec) of NTSC (National Television System Committee) signal or 50 Hz (approximately 20.0 msec) of PAL (Phase Alternation by Line). In order to meet the requirements of further market expansion, higher performance is required.
In view of this, conventionally, a liquid crystal display apparatus has been being developed whose response speed is increased by elaborating liquid crystal material and a method for driving a display.
For example, Patent Document 1 (Japanese Unexamined Patent Publication No. 39837/1998 (Tokukaihei 10-39837; published on Feb. 13, 1998)) discloses a liquid crystal display apparatus using “overshoot driving”. According to the liquid crystal display apparatus, a voltage greater than a voltage difference corresponding a change in gradation is applied so that the liquid crystal material is rapidly moved to a target gradation. According to the overshoot driving, a look-up table (LUT) is prepared in advance in which an applied gradation value (or an applied voltage value that realizes the applied gradation) to be applied to the liquid crystal material is set in association with an initial gradation (current gradation) and a target gradation (desired gradation), and a voltage is applied in accordance with the LUT.
However, an attempt to prepare an LUT in which values corresponding to applied voltage values corresponding to all patterns of gradation change are stored causes such a problem that a memory is required to have extremely large capacity to store the LUT.
In order to solve this problem, Patent Document 2 (Japanese Unexamined Patent Application No. 4629/2004 (Tokukai 2004-4629; published on Jan. 8, 2004) discloses a liquid crystal display apparatus. As shown in FIG. 9, the liquid crystal display apparatus includes an applied gradation value acquisition section 113 which receives previous gradation data, subsequent gradation data, and measurement data sent from a temperature sensor 108, and which, by making an interpolation calculation with reference to a plurality of LUTs stored in an LUT memory 112, calculates gradation data necessary for gradation display as target gradation data. This arrangement makes it possible that high-precision target gradation data (interpolated value) can be found, in consideration of various additional conditions, by interpolation calculation using a local coordinate.
However, whereas the arrangement of Patent Document 2 achieves a larger reduction in circuit size than the arrangement in which all the patterns are stored, the arrangement of Patent Document 2 suffers from a certain level of deterioration in display quality due to interpolation calculation as compared with the arrangement in which all the patterns are stored. This has made it necessary to further improve display quality so as not to cause a great increase in circuit size.